feat(issue-18): decide liveness and delivery by the event protocol, not the screen

Contract (no new event types): heartbeat every N s (automatic timer),
unresponsive after K x N s without an event, `started` within T s of the
injection, retained per-job state, and a remote transport.

- registry: heartbeat_sec / heartbeat_misses / ack_timeout_sec / transport
  fields; idle_timeout_sec derives K x N unless explicit (defaults 30/4/60
  keep the historical 120 s idle window).
- heartbeat.py + publish_event --heartbeat N: detached fixed-cadence timer
  publishing signed `progress` heartbeats (threaded wire publish, local
  record first); stopped by the terminal event via pidfile, by re-dispatch
  and by lifetime. Terminal events refuse --heartbeat.
- publish_event: retained `<prefix>/state` (status, last_event, seq, HMAC)
  sent on the same connection after every event (--no-state to skip);
  publisher.publish_raw takes extra messages.
- job_subscriber: subscribes the state topic, recovers terminal status from
  retained state, resets idle on any accepted message, records seq_gap and
  reconnected in the audit log, idle budget before the first event is
  T + K x N (--ack-timeout), --remote mirrors started/terminal events into
  the registry through the transition boundary.
- lib.sh send_keys_safe: an accepted-but-unconfirmed submission is confirmed
  by agent_status working or the job's own `started` (_sks_job_started);
  pane change and busy token are no longer delivery signals.
- wrapper: --heartbeat/--heartbeat-misses/--ack-timeout (MAM_* env),
  injected start command arms the timer, brief states the contract,
  _wait_started (registry / events.log / subscriber log, bounded by T and
  the wall clock) replaces the 10 s inject grace, R1 grace uses only the
  on-disk event age (herdr/pane logged once as a diagnostic),
  remote:<name> sessions skip preflight/idle/pane and dispatch over the
  broker (remote_dispatch).
- remote.py (+ scripts shim): signed retained dispatch (MAM_DISPATCH_SECRET)
  and a runner that mirrors the job into its own registry with the
  orchestrator's identity, publishes started --heartbeat, runs --exec and
  publishes the terminal event.
- loop runner: passes MAM_HEARTBEAT_SEC / MAM_HEARTBEAT_MISSES /
  MAM_ACK_TIMEOUT_S through; YAML rows with transport: remote delegate as
  remote:<name>.
- docs: MESSAGING.md 2.5 contract + remote transport, delegate-job SKILL.md,
  registry.md, loop SKILL.md.
- tests: tests/test_issue18_liveness_contract.py (16); issue 14 pane-signal
  tests flipped to started-based; issue 6 working-agent tests acknowledge
  with started; CLI snapshot/help captures refreshed.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/lib_py/delegation/publisher.py

@@ -79,11 +79,13 @@ class OneShotPublisher(_BasePublisher):
     def publish(self, prepared):
         self.publish_raw(prepared.config, prepared.topic, prepared.body, prepared.retain)
 
-    def publish_raw(self, config, topic: str, body: bytes, retain: bool) -> None:
+    def publish_raw(self, config, topic: str, body: bytes, retain: bool, extra=()) -> None:
         """Connect, publish, wait for the ACK, disconnect.
 
         The single implementation of one-shot publishing: ``publish_event``'s
         CLI path calls straight into this, so the two entry points cannot drift.
+        ``extra`` messages (``(topic, body, retain)`` tuples, Issue #18's retained
+        job state) go out over the same connection, each awaited like the first.
         """
         client = self.client_factory("publisher", config)
         self.connect_count += 1
@@ -104,6 +106,8 @@ class OneShotPublisher(_BasePublisher):
             if mqtt_common.reason_code_value(connected["rc"]) != 0:
                 raise ConnectionError("broker refused connection: rc={}".format(connected["rc"]))
             _send(client, topic, body, retain)
+            for x_topic, x_body, x_retain in (extra or ()):
+                _send(client, x_topic, x_body, x_retain)
         finally:
             client.loop_stop()
             try: